In many cooling systems associated with internal combustion engines, there is a requirement to control the flow of coolant in either a bypass loop or control the flow of coolant that goes into a core for a heater. This coolant flow control is currently performed with any of four (4) primary valve structures that can be driven by any one of five (5) valve control mechanisms.
In circumstances where the flow of coolant in either the bypass loop or the heater valve only needs to be turned on or turned off, a butterfly valve, a barrel valve, a poppet valve or a gate valve is typically utilized. However, when a variable flow of coolant in either the bypass loop or the heater valve is required, then only a barrel valve or a gate valve is utilized. There are five (5) mechanisms or techniques for operating the valves used in regulating the flow of coolant in either the bypass loop or the heater valve. The first mechanism is a direct mechanical linkage that is manually operated by the driver of the vehicle from the passenger compartment. The second mechanism is a blend door actuator that opens or closes a valve that is driven by a mechanical linkage. The blend door actuator functions much like an electronic temperature control system and controls the temperature. The blend door actuator controls the heat/cooling by monitoring a feedback signal from the temperature selector and electrically adjusts the blend door by means of an electric motor connected to a mechanical linkage to satisfy the request. The third mechanism is an auxiliary vacuum actuator that can position a valve in either two or three positions. The fourth mechanism utilizes a direct current (DC) motor and gear train with a feedback mechanism to indicate the variable position of a valve. Finally, the fifth mechanism is to use a direct solenoid drive to open and close a valve. This is utilized almost exclusively with poppet-type valves.
There are a number of limitations with these valves and valve control mechanisms. One significant limitation is that these valves need to be able to precisely control coolant flow in low flow ranges as well as being able to open fully to minimize pressure drop when full flow conditions are required. Poppet valves and butterfly valves provide a significant disadvantage regarding pressure drop since their flow control members remain in the flow path during full flow conditions. Barrel valves are typically used for variable flow, however, due to the geometric limitations of the barrel valve, the limited flow metering capability of the barrel valve is often gained at the expense of having adequate overall coolant flow through the barrel valve. Although gate valves can provide fine metered flow and do provide minimal pressure drop at full flow conditions, there are significant problems in size that restrict implementation in an automotive/vehicle coolant system.
Each one of the previously described valve control mechanisms has significant disadvantages. The direct mechanical linkage does not provide direct control of the valve in relation to the other heating, ventilating and air conditioning (HVAC) components in the vehicle. The indirect control of the valve via the blend door actuator also does not provide direct control of the valve in relation to the other heating, ventilating and air conditioning (HVAC) components in the vehicle. The auxiliary vacuum actuator is limited to two (2) or three (3) positions. This is of very limited value in a coolant flow control application. The direct current (DC) motor and gear train require auxiliary feedback electronics. This typically includes a potentiometer and onboard electronics to control position of the valve. This type of feedback circuit can be expensive and prone to problems due to the heat and other environmental factors associated with the vehicle. A direct solenoid control limits the valve to a two (2) position device. In order to provide flow control, the solenoid control needs to be pulsed on and off. This can create the undesirable effect of “hammering.” Hammering is a phenomenon that may cause damage to a valve or cause it to fail in delivering its main function. The unstable opening and closing of a valve reveals a shortcoming in the ability to maintain constant coolant flow velocity and effective closing. Solenoid controls also have the very undesirable effect of drawing a large amount of current.
In many situations when the internal combustion engine is cooling, it is desirable for the valve to return to a full open (fail-safe) position when the operating signal to the valve is lost. Universally, all valves that are operated by a mechanical linkage fail to have this type of feature. Electrically actuated valves that are driven by a direct current (DC) motor and a gear train require an external spring or possibly a clutch mechanism to accomplish this task. Both of these additional components are undesirable since both components can fail and are difficult to replace.
The present invention is directed to overcoming one or more of the problems set forth above.